feat(xlsx): make Excel export production-grade

- Add merge cells for project/version groups.
- Add numeric Hours column and human-readable Spent Time.
- Add version/project/grand totals.
- Apply auto-width, freeze panes, auto-filter and styling.
- Respect --no-time: keep columns empty, skip totals.
- Pass no_time flag through formatter factory to all file formatters.
- Add tests for XLSX features and --no-time behavior.

Closes #38

redmine_reporter/cli.py

@@ -145,6 +145,7 @@ def main(argv: Optional[List[str]] = None) -> int:
             author=Config.get_author(args.author),
             from_date=from_date,
             to_date=to_date,
+            no_time=args.no_time,
         )
 
         if not formatter: